Luca wrote:> On 6/11/07, Avi Kivity <avi@qumranet.com> wrote:>> Luca wrote:>> >>>> >> I've managed to reproduce this on kvm-21 (it takes many boots for>> this>> >> to happen, but it does eventually).>> >>> > Hum, any clue on the cause?>>>> From what I've seen, it's the new Linux clocksource code.>> Actually I tried forcing the PIT (and any other combination of> tsc,acpi_pm,jiffies) as the clocksource, without success.>

Well, there's lots of APIC stuff going on when it hangs.

>> > Should I test older versions?>>>> They're unlikely to be better. Instead, it would be best to see what>> the guest is doing.>>>> I suggest downloading the source rpm for the kernel, building it, and>> sprinkling printk()s until we know exactly what source the guest is>> executing at the time of the hang.>> Ok, will do. Meanwhile I discovered that the kernel on the boot cd> (the one that hangs) is compiled for i586, while the one installed on> disk is for i686 (this one works).

Ah.

>> i686 has this options enabled:>> +CONFIG_X86_GOOD_APIC=y> +CONFIG_X86_USE_PPRO_CHECKSUM=y> +CONFIG_X86_TSC=y>> but disabling tsc on the command line doesn't make any difference. Is> it possible that KVM is choking on some instruction not used by the> i686 kernel?

Unlikely, as then the hang would occur all the time instead of randomly.

-- Do not meddle in the internals of kernels, for they are subtle and quick to panic.